The deal raises Bombardier's firm order backlog for the CSeries to 177 jets and marks the largest acquisition by the Moscow-based lessor of Western aircraft.

"This is a landmark order for Bombardier Aerospace and its CSeries aircraft, as well as for this premier Russian leasing company," Mike Arcamone, president of Bombardier Commercial Aircraft, says in a statement.

IFC signed a letter of intent to buy 30 CS300s with 10 options at the Moscow air show (MAKS) in August 2011. Last February, IFC signed a purchase agreement raising the potential firm order to 32 aircraft. The deal still required approval by IFC shareholders, which includes rival jet maker Sukhoi.

To finalise the deal, IFC was forced in March to explain how the CSeries acquisition would not jeopardise the Russian aircraft manufacturing industry.

IFC officials have said that the CS300 fits in a niche between the larger Irkut MC-21 and the smaller Sukhoi Superjet. IFC also plans to market the CS300s to carriers outside of Russia, especially in the Commonwealth of Independent States (CIS).

The total deal for 42 CS300s including options is valued at $3.42 billion.

Two years ago, IFC says it was negotiating for a role in the CSeries product support system as part of the deal, but Bombardier's announcement of the finalised order did not mention such a role for the leasing company.